Compressive Failure Mechanism and Impact Behavior of Unidirectional Carbon-Fiber/Vinyl Ester Composites

Compressive failure of carbon fiber reinforced unidirectional vinyl ester composites (CFRP) under impact is studied experimentally and analytically. Both impact and quasi-static compressive tests are carried out for CFRP with Vf= 10% to 60%. Stress-stain curves at strain rates of 10-3 s-1 and 10-3 s-1 are obtained. The compressive strength increases under impact loading. As the fiber volume fraction increases, the failure mode changes from shear failure to kinking. The local stress fields in the fiber and matrix are analysed to illustrate the deformation and compressive failure mechanisms for unidirectional composites. Based on analysing the local matrix yield at the fiber-matrix interface due to shear stress concentration, the compressive strength is predicted. Assuming that shear failure and kinking occurs on the plane of the maximum shear strain in composites, the angle of the plane of the maximum shear strain is determined. The analytical model is utilised to explain the various experimental observations of CFRP failure, as well as GFRP failure reported in Reference [17], such as, the compressive strength, the failure mode, the effects of fiber volume fractions and strain rates.